A problem upon which the present invention is based is explained as an example, with reference to an ultrasonic detection system for vehicle surroundings.
German Patent Application No. DE 198 02 724 describes a transmitter which emits a modulated carrier signal having a characteristic signal shape. The signal is reflected from an object. A receiver detects the reception of the reflected signal and determines the time period between transmission and reception. The distance from the object is determined taking the speed of sound into account.
Updating of the distance is limited by necessary transmission pauses between the signals. The transmission pauses are typically 30 ms long. The position of the object during the transmission pause may be determined by extrapolating the motion of the object. However, this results in considerable inaccuracy in determining the speed, in particular due to the fact that an association of reflecting points with echoes may be incorrect.